Multiple Bank Flattened Tube Heat Exchanger

ABSTRACT

A multiple bank, flattened tube, finned heat exchanger includes a first tube bank including a plurality of flattened heat exchange tube segments extending longitudinally and arrayed in spaced parallel relationship between a first manifold and a second manifold and a second tube bank including a plurality of flattened tube segments extending longitudinally and arrayed in spaced parallel relationship between a first manifold and a second manifold, the second tube bank disposed in spaced relationship with and behind the first tube bank. A folded fin is disposed between each set of adjacent heat exchange tube segments of the first and second tube banks. Each folded fin extends between a respective set of adjacent heat exchange tube segments of both the first tube bank and the second tube bank, spanning the spacing gap between the tube banks. A plurality of fin notches protrude outwardly from each folded fin into the spacing gap.

BACKGROUND OF THE DISCLOSURE

This invention relates generally to heat exchangers and, more particularly, to multiple tube bank, flattened tube, finned heat exchangers.

Heat exchangers have long been used as evaporators and condensers in heating, ventilating, air conditioning and refrigeration (HVACR) applications. Historically, these heat exchangers have been round tube and plate fin (RTPF) heat exchangers. However, all-aluminum flattened tube plate fin heat exchangers are finding increasingly wider use in industry, including the HVACR industry, due to their compactness, thermal-hydraulic performance, structural rigidity, lower weight and reduced refrigerant charge, in comparison to conventional RTPF heat exchangers. Flattened tubes commonly used in HVACR applications typically have an interior subdivided into a plurality of parallel flow channels. Such flattened tubes are commonly referred to in the art as multi-channel tubes, mini-channel tubes or micro-channel tubes.

A typical flattened tube, finned heat exchanger includes a first manifold, a second manifold, and a single tube bank formed of a plurality of longitudinally extending flattened heat exchange tubes disposed in spaced parallel relationship and extending between the first manifold and the second manifold. The first manifold, second manifold and tube bank assembly is commonly referred to in the heat exchanger art as a slab. Additionally, a plurality of fins are disposed between the neighboring pairs of heat exchange tubes for increasing heat transfer between a fluid, commonly air in HVACR applications, flowing over the outer surface of the flattened tubes and along the fin surfaces and a fluid, commonly refrigerant in HVACR applications, flowing inside the flattened tubes. Such single tube bank heat exchangers, also known as single slab heat exchangers, have a pure cross-flow configuration.

Double bank flattened tube and fin heat exchangers are also known in the art. In conventional double bank flattened tube and fin heat exchangers are typically formed of two conventional fin and tube slabs, one spaced behind the other. A challenge in manufacturing multiple bank heat exchangers is maintaining a desired spacing between the individual tube banks, particularly during the manufacture assembly and furnace brazing of the multiple bank heat exchanger.

SUMMARY OF THE INVENTION

A multiple bank, flattened tube and folded fin heat exchange unit is provided wherein spacing between tube banks is achieved by a fin notch protruding outwardly from the fin caps of folded fin(s) into a gap between the trailing edges of the heat exchange tube segments of a first tube bank and the leading edges of the heat exchange tube segments of a second tube bank disposed next rearward of the first tube bank. The fin notch has a notch width defining the desired depth of the gap to be maintained between the two tube banks. The fin notch may have a notch height equal to at least one half of the thickness of the flattened tube heat exchange tube segments. In an embodiment, the fin notch may have a notch height in range from at least one half of the thickness of the flattened heat exchange tube segments to equal to the thickness of the flattened heat exchange tube segments. In an embodiment, the fin notch may have a notch height in range from at least one half of the thickness of the flattened heat exchange tube segments to less than the thickness of the flattened heat exchange tube segments.

BRIEF DESCRIPTION OF THE DRAWINGS

For a further understanding of the disclosure, reference will be made to the following detailed description which is to be read in connection with the accompanying drawing, where:

FIG. 1 is a diagrammatic illustration of an embodiment of a multiple tube bank, flattened tube finned heat exchange unit as disclosed herein;

FIG. 2 is a top, plan view, partly in section, of the embodiment of the multiple tube bank, flattened tube finned heat exchange unit of FIG. 1;

FIG. 3 is a sectioned side elevation view of the embodiment of the multiple tube bank, flattened tube finned heat exchange unit of FIG. 1;

FIG. 4 is a diagrammatic frontal elevation view of a segment of an embodiment of the folded fin of FIG. 3 having an embodiment of fin notches as disclosed herein;

FIG. 5 is a perspective view of a segment of the embodiment of the folded fin of FIG. 4;

FIG. 6 is a perspective view of a fin notch of the folded fin of FIG. 4;

FIG. 7 is an exploded view illustrating assembly of the multiple tube bank, flattened tube finned heat exchanger unit of FIG. 1 incorporating the embodiment of the folded fin of FIG. 4;

FIG. 8 is a perspective view of a segment of an embodiment of the folded fin of FIG. 3 having another embodiment of fin notches as disclosed herein; and

FIG. 9 is a perspective view of a segment of an embodiment of a folded fin having another embodiment of fin notches as disclosed herein.

DETAILED DESCRIPTION

An exemplary embodiment of a multiple bank flattened tube finned heat exchanger unit, generally designated 10, in accordance with the disclosure is depicted in FIGS. 1, 2 and 3. As depicted therein, the multiple bank flattened tube finned heat exchanger 10 includes a first tube bank 100 and a second tube bank 200 that is disposed behind the first tube bank 100, that is downstream with respect to the air flow, A, through the heat exchanger. The first tube bank 100 may also be referred to herein as the front heat exchanger slab 100 and the second tube bank 200 may also be referred to herein as the rear heat exchanger slab 200.

The first tube bank 100 includes a first manifold 102, a second manifold 104 spaced apart from the first manifold 102, and a plurality of heat exchange tube segments 106, including at least a first and a second tube segment, extending longitudinally in spaced parallel relationship between and connecting the first manifold 102 and the second manifold 104 in fluid communication. The second tube bank 200 includes a first manifold 202, a second manifold 204 spaced apart from the first manifold 202, and a plurality of heat exchange tube segments 206, including at least a first and a second tube segment, extending longitudinally in spaced parallel relationship between and connecting the first manifold 202 and the second manifold 204 in fluid communication. The second tube bank 200 is disposed in alignment with the first tube bank 100 whereby the heat exchange tube segments 206 of the second tube bank 200 aligned with the heat exchange tube segments 106 of the first tube bank 100, for example as illustrated in FIG. 3.

Referring in particular to FIG. 3, each of the heat exchange tube segments 106, 206 comprises a flattened heat exchange tube having a leading edge 108, 208, a trailing edge 110, 210, an upper flat surface 112, 212, and a lower flat surface 114, 214. The leading edge 108, 208 of each heat exchange tube segment 106, 206 is upstream of its respective trailing edge 110, 210 with respect to the airflow through the heat exchanger 10. In the embodiment depicted in FIG. 3, the respective leading and trailing portions of the flattened tube segments 106, 206 are rounded thereby providing blunt leading edges 108, 208 and trailing edges 110, 210. However, it is to be understood that the respective leading and trailing portions of the flattened tube segments 106, 206 may be formed in other configurations. The second tube bank 200 is spaced behind the first tube bank 100 with the leading edge 208 of each of the heat exchange tube segments 206 of the second tube bank 200 spaced from the trailing edge 110 of each of the heat exchange tube segments 106 of the first tube bank 100 at a desired spacing gap 15.

The interior flow passage of each of the heat exchange tube segments 106, 206 of the first and second tube banks 100, 200, respectively, may be divided by interior walls into a plurality of discrete flow channels 116, 216 that extend longitudinally the length of the tube from an inlet end of the tube to an outlet end of the tube and establish fluid communication between the respective headers of the first and the second tube banks 100, 200. The flow channels 116, 216 provide a plurality of flow paths through which refrigerant, R, may pass between the manifolds 102, 104 and 202, 204, respectively, in heat exchange relationship with the air flow, A, passing over the outer surfaces of the heat exchange tube segments 106, 206. The flow channels 116, 216 may have a circular cross-section, a rectangular cross-section or other non-circular cross-section. Also, the interior flow passages of the heat exchange tube segments 106, 206 may be divided into the same or into a different number of discrete flow channels 116, 216.

In the embodiment of the multi-channel heat exchange tube segments 106, 206 depicted in FIG. 3, the heat exchange tube segments 106 of the first tube bank 100 have a depth, that is an expanse in a direction perpendicularly traverse to the longitudinal axes of the parallel heat exchange tube segments 106, 206, that is different, it this embodiment less than, than the depth of the heat exchange tube segments 206 of the second bank. However, it is to be understood that the depth of the heat exchange segments 106 and 206 may be the same, or the depth of the heat exchange tube segments 106 of the first tube bank 100 may be greater than the depth of the heat exchange segments 206 of the second tube bank 200.

In the embodiment of the multiple bank, flattened tube heat exchanger depicted in the drawings, the heat exchange tube segments 106, 206 comprise a plurality of parallel linear segments wherein each individual segment connects directing to a manifold at each end. However, it is to be understood that the tube banks 100, 200 could include serpentine tubes with the heat exchange tube segments 106, 206 being parallel linear tube segments connected by U-bends or hairpin turns to form a serpentine tube connected at its respective ends between the spaced manifolds of the tube bank.

The multiple bank, flattened tube heat exchanger 10 disclosed herein further includes a plurality of folded fins 20. Each folded fin 20 is formed, for example by stamping a continuous sheet of fin material, such as for example aluminum or an aluminum alloy, in a serpentine, ribbon-like fashion thereby providing a plurality of fin faces 22 connected together by fin caps 24. For example, as illustrated diagrammatically in FIG. 4, in an embodiment, the folded fin 20 includes a plurality of spaced parallel fin faces 22 interconnected at their ends up fin caps 24 to form a continuous serpentine ribbon-like folded fin. It is understood, however, that in other embodiments of the folded fin 20, the fin faces 22 may extend obliquely, rather than parallel.

A longitudinally extending folded fin 20 is disposed between each pair of neighboring heat exchange tube segments 106 of the first tube bank 100 and an aligned pair of neighboring heat exchange tube segments 206 of the second tube bank 200. Each folded fin 20 extends longitudinally, that is along the longitudinal axes of the heat exchange tube segments 106, 206, and transversely, that is perpendicularly to the longitudinal axes of the heat exchange tube segments 106, 206. Folded fins 20 are disposed between each pair of neighboring heat exchange tubes 106, 206 across the width of the effective heat transfer area of the heat exchanger unit 10 whereby the air flow, A, passing through the heat exchanger unit 10 passes over the surfaces of the fin faces 22. Each folded fin 20 is disposed between a respective pair of neighboring tube segments 106 and a respective pair of heat exchange tube segments 206 with the end caps 24 on opposite sides of the folded fin 20 in contact with the faces 112, 212 and 114, 214, respectively, of the heat exchange tube segments.

As depicted in FIG. 3, the fin faces 22 and the fin caps 24 of the folded fins 20 extend along the depth of the multiple bank, flattened tube heat exchanger 10 between a first heat exchange tube segment 106 and a second neighboring heat exchange tube segment 106 of the first tube bank 100, span the spacing gap 15 between the trailing edges 110 heat exchange tube segments 106 of the first tube bank 100 and the leading edges 208 of the heat exchange tube segments 206 of the second tube bank 200, and thence extend between a first heat exchange tube segment 206 and a neighboring second heat exchange tube segment 206 of the second tube bank 200. The folded fin 20 may include a plurality of louvers 40 cut in the fin faces 22, for example as disclosed in International Patent Application No. PCT/US2011/0060506, filed 14 Nov. 2011, and published 31 May 2012 as International Publication No. WO 2012/071196 A2, which publication is incorporated herein in its entirety.

In the embodiment depicted in FIG. 3, the fin faces 22 and the fin caps 24 of the folded fins 20 extend the full depth of the heat exchanger 10 from the leading edges 108 of the heat exchange tube segments 106 of the first (i.e. forward) tube bank 100 to the trailing edges 210 of the heat exchange tube segments 206 of the second (i.e. aft) tube bank 200. However, it is to be understood that the folded fins may overhang the leading edges 108 of the heat exchange tube segments 106 of the first tube bank 100 and/or overhang the trailing edges 210 of the heat exchange tube segments 206 of the second tube bank 200.

Additionally, each folded fin 20 includes a plurality of fin notches 26 that protrude outwardly from the fin caps 24 of the folded fin 20 into the spacing gap 15 between the trailing edge 110 of the heat exchange tube segment 106 of the first tube bank 100 and the leading edge 208 of the heat exchange tube segment 206 of the second tube bank 200 aligned therewith. The fin notches 26 extending into the spacing gap 15 defines the depth of the spacing gap 15 and maintains the spacing gap 15 at that depth during assembly and brazing of the heat exchanger unit 10. In an embodiment, an outwardly protruding fin notch 26 is provided on each fin cap 24. However it is to be understood that in other embodiments of the multiple bank flattened tube heat exchanger unit 10 disclosed herein, some plurality of caps 24 less than all the caps 24 have a fin notch 26 formed therein.

Referring now to FIGS. 4-8, each fin notch 26 has a dimension 28 defining the depth of the spacing gap 15 between the trailing edge 110 of the heat exchange tube segment 106 of the first tube bank 100 and the leading edge 208 of the heat exchange tube segment 206 of the second tube bank 200. Each fin notch 26 has a height 30, that is a dimension defining the extent to which the fin notch 26 protrudes outwardly from the surface of the fin cap 24. In an embodiment, the fin height 30 is at least equal to one-half the thickness of the heat exchange tube segments 106, 206. In an embodiment, the fin height 30 may be in the range from at least one-half the thickness of the heat exchange tube segments 106, 206 to the full thickness of the heat exchange tube segments 106, 206.

In the embodiment of the folded fin 26 as depicted in FIGS. 4-6, each notch 26 is formed in a respective fin cap 24 as a unbroken tent-like notch that protrudes outwardly from the fin cap 24, having the desired fin height 30 as measured from the fin cap 24 to the apex of the unbroken fin notch 26. The unbroken fin 26 may be formed simultaneously with formation of the folded fin 20 during a rolling process or a stamping process, or may be stamped in the fin caps 24 in a secondary operation after formation of folded fin 20. In the embodiments depicted in FIGS. 8 and 9, each notch 26 is formed in a respective fin cap 24 as a broken notch having two generally vertically, spaced, outwardly extending sides the protrude outwardly from the fin cap 24, the sides having the desired fin height 30. In the embodiment depicted in FIG. 8, the sides of the broken notch 26 have a dimension 28 extending along the fin cap 24 defining the depth of the spacing gap 15. In the embodiment depicted in FIG. 9, the sides of the broken notch 26 are spaced at a dimension 28 defining the depth of the spacing gap 15. The broken notches 26 may be formed, for example, in a secondary operation, for example stamping, after the folded fin 20 has been formed in a rolling process.

Referring now to FIG. 7, during manufacture of the multiple bank flattened tube heat exchanger 10 disclosed herein, the multiple tube bank assembly may be constructed by first laying down a base heat exchange tube segment 106 and a base heat exchange tube segment 206 in parallel spaced relationship at the desired spacing gap, then installing a folded fin 20 on the base heat exchange tube segments 106, 206, with the fin notches 26 protruding from the fin caps 24 on one side 32 of the folded fin 20 extending into the spacing gap 15. Next, a second aligned pair of heat exchange tube segments 106, 206 is laid upon the folded fin 20 with the trailing edge 110 of the heat exchange tube segment 106 and the leading edge 208 of the heat exchange tube segment 206 abutting the fin notches 26 protruding from the fin caps 24 on the other side 34 of folded fin 20. The remainder of the tube bank assembly is built up of alternating folded fins 20 and aligned tubes 106, 206 in this manner. The assembled tube bank is wrapped with wire or clipped by the frame clips to temporary hold the tube bank assembly together and the manifolds 102, 104, 202 and 204 are then mounted to the tube bank assembly. A suitable brazing compound is applied as appropriate the various components of the assembly and the entire assembly is placed into and heated in a brazing furnace.

During the brazing process of the assembled heat exchanger, the folded fins 20 are metallurgically bonded to the heat exchange tube segments 106, 206 with the fin notches 26 establishing the desired spacing gap 15 between the heat exchange tube segments 106 of the first tube bank 100 and the heat exchange tube segments 206 of the second tube bank 200. The fin notches 26 serve to maintain that desired spacing gap and provide additional structural rigidity during shipment, site installation, and operation of the multiple bank, flattened tube heat exchanger 10.

Additionally, an opening 36 formed in the fin cap 24 upon stamping of the fin notch 26 provides a condensate/moisture drainage opening through which water collecting on the heat exchange tube segments 106 and fin faces 22 during application may drain from the heat exchanger 10. The opening 36 formed in the fin cap 24 upon stamping of the fin notch 26 also interrupts a heat conductive flow path along the fin cap 24, thereby reducing heat conduction between the heat exchange tube segments 106 of the first tube bank 100 and the respective aligned heat exchange tube segments 206 of the second tube bank 200.

Although depicted as having two tube banks, it is to be understood that the multiple bank flattened tube heat exchanger 10 disclosed herein may include a third tube bank, or even more tube banks, incorporating folded fins 20 that extend across all tube banks of the multiple bank heat exchanger and include fin notches 26 on the end caps 24 that protrude outwardly into the spacing gaps between the respective trailing edge of each forward tube bank and the leading edge of the next aft tube bank.

While the present invention has been particularly shown and described with reference to the exemplary embodiments as illustrated in the drawing, it will be recognized by those skilled in the art that various modifications may be made without departing from the spirit and scope of the invention. Therefore, it is intended that the present disclosure not be limited to the particular embodiment(s) disclosed as, but that the disclosure will include all embodiments falling within the scope of the appended claims. 

1. A multiple bank, flattened tube heat exchanger comprising: a first tube bank including at least a first flattened heat exchange tube segment and a second flattened heat exchange tube segment extending longitudinally and arrayed in spaced parallel relationship between a first manifold and a second manifold; a second tube bank including at least a first flattened heat exchange tube segment and a second flattened heat exchange tube segment extending longitudinally and arrayed in spaced parallel relationship between a first manifold and a second manifold, the second tube bank disposed in spaced relationship at a spacing gap behind the first tube bank; a longitudinally extending folded fin disposed between said first and second heat exchange tube segments of the first tube bank and between said first and second heat exchange tube segments of the second tube bank and spanning said spacing gap, said folded fin having a plurality of spaced fin faces extending between said first and second heat exchange tube segments of the first tube bank and between said first and second heat exchange tube segments of the second tube bank and a plurality of fin caps interconnecting the fin faces and abutting said first and second heat exchange tube segments of the first tube bank and said first and second heat exchange tube segments of the second tube bank; and a plurality of fin notches protruding outwardly from said folded fin into said spacing gap, each fin notch protruding outwardly from a respective one of said plurality of fin caps into said spacing gap; wherein each fin notch has a height equal to at least a half of a thickness of said heat transfer tube segments.
 2. The heat exchanger of claim 1 wherein each fin notch has a dimension defining the width of said spacing gap.
 3. (canceled)
 4. The heat exchanger of claim 1 wherein each fin notch has a height in the range from at least a half of the thickness of said heat transfer tube segments up to the thickness of the heat transfer tube segments.
 5. The heat exchanger of claim 1 wherein each fin notch has a height in the range from at least a half of the thickness of said heat transfer tube segments to less than the thickness of the heat transfer tube segments.
 6. The heat exchanger of claim 1 wherein a fin notch in provided in each fin cap of the plurality of fin caps of said folded fin.
 7. The heat exchanger of claim 1 wherein each fin notch is formed during a process of rolling said folded fin from a sheet of fin material.
 8. The heat exchanger of claim 7 wherein each fin notch is formed by stamping said folded fin.
 9. The heat exchange of claim 7 wherein the sheet of fin material comprises a ribbon of aluminum or an aluminum alloy material.
 10. The heat exchanger of claim 1 wherein each notch further defines an opening in a portion of a respective fin cap spanning the spacing gap, the opening in the fin cap disrupting conductive heat transfer between the abutting heat exchange tube segments of the first and second heat exchange tube banks.
 11. The heat exchanger of claim 1 wherein each notch further defines an opening in a portion of a respective fin cap spanning the spacing gap, the opening in the cap providing a condensate drain port.
 12. The heat exchanger of claim 1 wherein each notch further provides additional structural rigidity to said heat exchanger.
 13. The heat exchanger of claim 1 wherein each notch interrupts a heat conductive flow path along the fin cap of said folded.
 14. A multiple bank, flattened tube heat exchanger comprising: a first tube bank including a plurality of flattened heat exchange tube segments extending longitudinally and arrayed in spaced parallel relationship between a first manifold and a second manifold; a second tube bank including a plurality of flattened heat exchange tube segments extending longitudinally and arrayed in spaced parallel relationship between a first manifold and a second manifold, the second tube bank disposed in spaced relationship at a spacing gap behind the first tube bank with the arrayed plurality of heat exchange tube segments of the second bank aligned with the arrayed plurality of heat exchange tube segments of the first tube bank; a plurality of longitudinally extending folded fins with a folded fin disposed between each respective set of neighboring heat exchange tube segments of the first tube bank and between each respective aligned set of neighboring heat exchange tube segments of the second tube bank and spanning said spacing gap, each folded fin of said plurality of folded fins having a plurality of spaced fin faces extending between said first and second heat exchange tube segments of the first tube bank and between said first and second heat exchange tube segments of the second tube bank and a plurality of fin caps interconnecting the fin faces and abutting said aligned sets of heat exchange tube segments of the first tube bank and the second tube bank; and a fin notch protruding outwardly from at least some of the fin caps of each fin of said plurality of folded fins into said spacing gap; wherein each fin notch has a height equal to at least a half of a thickness of said heat transfer tube segments. 